On one hand, a Physical Downlink Share Channel (PDSCH) in a Long Term Evolution (LTE) system supports a Hybrid Automatic Repeat Request (HARQ) function. After establishing a communication connection with a base station, terminal equipment receives Downlink Control Information (DCI) and acquires scheduling information (which may include, for example, locations and the number of physical resource(s), a modulation and coding level and the like) corresponding to the PDSCH. The terminal equipment receives the PDSCH according to the scheduling information, and demodulates and decodes a Transport Block (TB) carried therein. If a decoding result is correct, the terminal equipment may feedback Acknowledgement (ACK) information to the base station. If the decoding result is incorrect, the terminal equipment may feedback Negative Acknowledgement (NACK) information to the base station, and then the base station retransmits the TB.
The ACK information or the NACK information may be transmitted through a Physical Uplink Share Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH). When the terminal equipment has no PUSCH transmitted in an uplink subframe, the ACK information or NACK transmitted in the subframe may only be transmitted through the PUCCH.
On the other hand, the LTE system may use a Carrier Aggregation (CA) technology to implement bandwidth extension, that is, multiple LTE Component Carriers (CCs) are aggregated to achieve a larger transmission bandwidth.
For the CA technology, a conventional art discloses a License Assisted Access (LAA) technology to implement aggregation of a licensed carrier and an unlicensed carrier. For an unlicensed carrier in an LAA system, the base station completes preparations (coding, modulation, resource mapping and the like) for data in a subframe, but it is uncertain about the specific subframe on which the data is transmitted, that is, the base station may not completely know about a scheduling condition on each carrier in any downlink subframe. Therefore, the base station may not set information in the DCI to indicate an amount of feedback information (ACK information or NACK information) required to be fed back by the terminal equipment, which lowers efficiency of feedback information transmission between the base station and the terminal equipment.